Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userDetermination of the trigonal warping orientation in Bernal-stacked bilayer graphene via scanning tunneling microscopy
66
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The existence of strong trigonal warping around the K point for the low energy electronic states in multilayer (N$geq$2) graphene films and graphite is well established. It is responsible for phenomena such as Lifshitz transitions and anisotropic ballistic transport. The absolute orientation of the trigonal warping with respect to the center of the Brillouin zone is however not agreed upon. Here, we use quasiparticle scattering experiments on a gated bilayer graphene/hexagonal boron nitride heterostructure to settle this disagreement. We compare Fourier transforms of scattering interference maps acquired at various energies away from the charge neutrality point with tight-binding-based joint density of states simulations. This comparison enables unambiguous determination of the trigonal warping orientation for bilayer graphene low energy states. Our experimental technique is promising for quasi-directly studying fine features of the band structure of gated two-dimensional materials such as topological transitions, interlayer hybridization, and moire minibands.
rate research
Read More
We calculate the form of quasiparticle interference patterns in bilayer graphene within a low-energy description, taking into account perturbatively the trigonal warping terms. We introduce four different types of impurities localized on the A and B sublattices of the first and the second layer, and we obtain closed-form analytical expressions both in real and Fourier spaces for the oscillatory corrections to the local density of states generated by the impurities. Finally, we compare our findings with recent experimental and semi-analytical T-matrix results from arXiv:2104.10620 and we show that there is a very good agreement between our findings and the previous results, as well as with the experimental data.
The low-frequency magneto-optical properties of bilayer Bernal graphene are studied by the tight-binding model with four most important interlayer interactions taken into account. Since the main features of the wave functions are well depicted, the Landau levels can be divided into two groups based on the characteristics of the wave functions. These Landau levels lead to four categories of absorption peaks in the optical absorption spectra. Such absorption peaks own complex optical selection rules and these rules can be reasonably explained by the characteristics of the wave functions. In addition, twin-peak structures, regular frequency-dependent absorption rates and complex field-dependent frequencies are also obtained in this work. The main features of the absorption peaks are very different from those in monolayer graphene and have their origin in the interlayer interactions.
We examine the quantum Hall effect in bilayer graphene grown on Cu substrates by chemical vapor deposition. Spatially resolved Raman spectroscopy suggests a mixture of Bernal (A-B) stacked and rotationally faulted (twisted) domains. Magnetotransport measurements performed on bilayer domains with a wide 2D band reveal quantum Hall states (QHSs) at filling factors $ u=4, 8, 12$ consistent with a Bernal stacked bilayer, while magnetotransport measurements in bilayer domains defined by a narrow 2D band show a superposition of QHSs of two independent monolayers. The analysis of the Shubnikov-de Haas oscillations measured in twisted graphene bilayers provides the carrier density in each layer as a function of the gate bias and the inter-layer capacitance.
The low-frequency magneto-optical absorption spectra of bilayer Bernal graphene are studied within the tight-binding model and gradient approximation. The interlayer interactions strongly affect the electronic properties of the Landau levels (LLs), and thus enrich the optical absorption spectra. According to the characteristics of the wave functions, the low-energy LLs can be divided into two groups. This division results in four kinds of optical absorption peaks with complex optical selection rules. Observing the experimental convergent absorption frequencies close to zero magnetic field might be useful and reliable in determining the values of several hopping integrals. The dependence of the optical absorption spectra on the field strength is investigated in detail, and the results differ considerably from those of monolayer graphene.
We study the superlattice minibands produced by the interplay between moire pattern induced by hexagonal BN substrate on graphene layer and the interlayer coupling in bilayer graphene with Bernal stacking (BLG). We compare moire miniband features in BLG, where they are affected by the interlayer asymmetry of BLG-hBN heterostructure and trigonal warping characteristic for electrons in Bernal-stacked bilayers with those found in monolayer graphene.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
